Intrauterine devices (IUDs) were once a very popular birth control method in the US; in the 1970s, nearly ten percent of contracepting women used them. The rapid decline in use is due in part to the safety concerns about devices that are no longer on the market. Less than one percent of US women use today's IUDs, yet there is great potential for attracting a new population of users if the negative image of past devices can be shed and if certain unfavorable method-specific features can be mitigated. Increased bleeding and pain are the most common complaints of IUD users; together these two side effects cause up to 15 percent of women to discontinue use within the first year. Ibuprofen is commonly used to treat IUD-induced bleeding and pain, though it is not routinely provided either at the time of insertion or as a take-home medication. If new users take ibuprofen before insertion and are given a supply of ibuprofen to take home, they may avoid discomforts that might otherwise lead to early removal. The primary objective of this study is to determine whether prophylactic use of ibuprofen affects continuation rates. The study will also measure the impact ibuprofen has on the distribution of reasons for IUD removal, the number of bleeding and pain events, and the number of unscheduled clinic visits. This is a double-blind randomized controlled trial of 2,258 first-time IUD users; half of the participants will receive ibuprofen and the other half will receive an identical-appearing placebo. Women will be given their first dose 45 minutes prior to insertion and asked to take the same medication over the 3-5 days of menses for each of their next six cycles. Though the intervention component of the study lasts only six months, the two groups of women will be followed up for twelve months to compare overall discontinuation rates, reasons for removal, level of pain at insertion, incidence of post-insertion bleeding and pain events, and the number of unscheduled clinic visits. If ibuprofen is found to have a beneficial effect on continuation rates, it can become a standard feature of product labeling; because ibuprofen is inexpensive, safe, and readily available in over-the-counter form, it could ultimately improve IUD comfort for 100 million women worldwide. In the US, ibuprofen may help spur renewed interest in the most cost effective and efficacious reversible contraceptive method available.